This invention relates to transport refrigeration systems. More particularly, this invention relates to a start up control for an all electric truck trailer refrigeration system that receives its compressor drive motor power and all other electrical power from a single on-board engine driven synchronous generator.
Transport refrigeration systems for a standardized truck trailer having onboard regulated power necessary to operate certain components such as system controls, motors and related devices are known in the art. Some of these refrigeration systems are also known to employ synchronous generators, such as that employed in the GOLDEN EAGLE transport refrigeration unit manufactured by the CARRIER TRANSICOLD DIVISION of the CARRIER CORPORATION of Farmington, Conn.
Equipment used in truck trailer refrigeration units must be accommodated within the limited space bounded by the tractor swing radius and the trailer front wall. In the prior art, such transport refrigeration applications have included an on-board, small power output generator or alternator and regulator apparatus which has been limited to providing power to a portion of the system power consuming apparatus, such as fan motors and system controls. On-board generators that are sufficiently large enough to simultaneously provide all the power needed by the transport refrigeration system, including the power to run compressor drive motor, have heretofore been too large to be accommodated within the aforementioned available space, and would also be too heavy and too costly even if they were available, for serious consideration for use in conventional truck trailer transport refrigeration systems.
Synchronous generators which are small enough to meet the aforementioned size and weight requirements, are not configured to meet the overall transport refrigeration system power requirements. Large synchronous generators of sufficient power capability to fully power a truck trailer transport refrigeration system have been too large, too heavy and too costly to meet on-board size and weight requirements. Therefore, use of conventional synchronous generators to provide the entire motor and control system power for transport refrigeration units has not heretofore been a viable option in the transport refrigeration industry.
Generally, transport refrigeration systems such as those used on truck trailers, have employed belt driven and/or mechanically linked shaft driven compressor units rather than electrical motor driven compressor units. Such systems have also usually included belt driven, or otherwise mechanically linked fan powering systems. Alternatively, various types of generators or alternators and regulator apparatus have provided a portion of the power required by the refrigeration system within a package size that is sufficiently small to meet the size constraints of trailer transport refrigeration systems. Conventional refrigeration system generator units have not been capable of generating sufficient output power to simultaneously power the compressor drive motor and all other motors and electrical devices of a transport refrigeration system. As a result, such systems have required compressor units which are driven, through a mechanical coupling, by an engine such as a diesel. The engine also drives the refrigeration system fans and other components through additional mechanical drives utilizing pulleys, v-belts and the like.
A disadvantage of these known engine driven refrigeration systems is the need to provide suitable coupling apparatus between the engine and the compressor and other mechanically linked apparatus, as stated herein above. Generally, the engine power is coupled to the compressor via a compressor drive shaft that necessarily requires a fluid tight shaft seal to ensure that refrigerant does not leak out of the compressor from around the drive shaft. In view of the above, those skilled in the art of transport refrigeration have been aware that the aforesaid drive shaft seals deteriorate with time and usage, resulting in loss of system refrigerant due to leakage around the compressor drive shaft, creating a long felt need for a viable solution to this problem. Further, the mechanical linkages introduce vibration to these systems, require a reservation of a routing path for the linkage between the engine and its powered units, and require a maintenance cost overhead, that would otherwise not be necessary.
A commonly assigned U.S. patent application Ser. No. 09/295,872 filed on even date herewith relates to a compact, light weight, all electric transport refrigeration system with on-board electrical power generating capacity which is capable of providing multi-phase and/or single-phase power to simultaneously supply the electrical requirements of the refrigeration system compressor motor as well as all other motors and electrical devices. Under certain operating conditions, such as start up and when the refrigerant is at high temperature and pressure levels, the power consumption of the compressor drive motor may exceed the power generating capacity of the generator. Accordingly, it is desirable to limit the power demands on the generator during such operating conditions.